EAGLE GROVE — The City of Eagle Grove was in a little bit of hot water with the Iowa Department of Natural Resources earlier this summer.

According to an administrative consent order between the city and the DNR, DNR staff conducted an inspection of the Eagle Grove wastewater treatment facility in August 2020. During this inspection, inspectors found that Prestage Foods of Iowa, a “significant industrial user” was in violation of its treatment agreement with the city and the city was in “substantial noncompliance with its nitrate effluent limit.”

According to Eagle Grove City Administrator Bryce Davis, the issue was mainly with the wastewater treatment facility being unable to treat the pretreated wastewater sent to it by Prestage.

Davis said the city’s National Pollution Discharge Elimination System, or NPDES, permit with the DNR is for 1,900 pounds per day of max loading of effluents like nitrogen, solids, ammonia nitrogen and more. Under the city’s NPDES permit, the city discharges treated wastewater to various drainage ditches, which ultimately flow to the Boone River.

Prestage’s agreement with the city allows the pork processing plant to send the city more than 1,600 pounds per day of total Kjeldahl nitrogen, or TKN. He said Prestage has been sending an average of 1,200 pounds per day of TKN, so they’ve been under their permitted levels for that.

“The problem that we face is in order to treat TKN, you have to have a carbon source,” Davis said. “Prestage, their pretreatment is an anaerobic lagoon system — it’s basically a DAF, which is dissolved air filtration, then it goes into a decanter to remove some solids, then it goes into an anaerobic lagoon system before it gets sent to us.”

That pretreatment focuses solely on carbon, Davis said, explaining that carbon is also later needed to treat the nitrogen and nitrates in the wastewater once it gets to the city’s treatment facility.

The Prestage plant is also required to send the city wastewater treatment plant 2,800 pounds per day of biochemical oxygen demand, or BOD, and it had been sending “much, much less,” Davis explained.

The BOD is needed to treat the TKD in the wastewater down to an acceptable level. To compensate, Eagle Grove has added supplemental carbon to its plant to raise the ratio of BOD to TKN concentration.

“We’ve worked well with Prestage,” Davis said. “They’ve streamlined their flow meter, which is basically sending us consistent flow over the week, which makes it easier to treat consistent water and get consistent results.”

Prestage has also added a second decanter, which has reduced the solids in the wastewater, which has saved the city on the back end from having to remove those solids, Davis said.

The wastewater treatment facility also had an aerator that was not working correctly, which contributed to its noncompliance with the DNR, the city administrator said.

Though the administrative consent order was signed June 8, the city had solved the issues and had been in compliance for about two months by that date, Davis said.

“Everything is fixed right now and we anticipate it to stay that way,” he said. “And we know what we need to do to move forward to ensure that it stays that way. Unfortunately, it’s going to cost money and it’s going to take time.”

As part of the administrative consent order, the city is also required to pay a $5,000 fine to the DNR. The order also requires the city complete construction of necessary upgrades to the wastewater treatment facility no later than Jan. 3, 2023.